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  1. #1

    Cooling at Night, Struggling During the Day

    Hey Guys,

    Thank you in advance for taking the time to read this and for any insight you may have.

    I have a 3300 sq foot house located in Los Angeles. The upstairs and downstairs each have a package unit.

    The upstairs unit is a 2 Ton Bryant that was installed at the end of 2000. The unit has a Honeywell Zone controller. 1 zone is the office, second zone is the master bedroom. Both zones total about 1000sq feet. The office houses racks of computers and requires AC year round to stay cool.

    When the system was installed (10 Years Ago) they system was able to alter the temperature in either zone at about a degree a minute.

    Over the past few months the master bedroom zone has been running longer and longer at night to cool the bedroom. Bedroom zone is set for 88 during the day and 78 at night. In the last couple of weeks the bedroom zone was running up to 1/2 an hour, off for 5-10 minutes and then back on. In addition it seemed there was less air flow, and I was concerned that the dampers might be failing. Each zone has multiple registers.

    I had changed out Air Filters, and figured I was due to clean the coils. They had never been done and I do lots of dusty Home Repair work.

    Then last Thursday the unit ran all night and wasn't able to pull the temp down under 88 degrees.

    So Friday I went up on the roof and opened it up. The coils were clean (very clean in fact) and the lower 1/3 of the coils were a frozen block of ice.

    I let the unit dethaw on Friday, and Friday night after checking it was thawed cranked it up and got mild cool air. However, the room was over 90 and the unit once again ran all night without being able to drop the temperature.

    On Saturday, my friend came over and put the gauges on the system. We ran the system and the pressure was initially outrageously high on both sides. When the system ran it immediately began freezing the bottom coils and the line coming out of the top of the compressor.

    After running for a bit the pressures settled down. Another friend who is an ESCO HVAC engineer stopped by and said the unit was probably low on R22. So we went out and picked up a tank. We added about 2 lbs of R22 (AC Unit holds 3.5). Then ran the system. The gauges read low, and now the coils on the bottom of the condenser, and on the top were freezing, but the middle ones were only collecting condensation.

    We let it run for about 20 minutes, and went inside and checked the air flow. The air was cool, but there wasn't much air flow.

    So we went back up on the roof, and checked the gauges and the system still showed a little low. We opened up the freon tap and after about a minute we stopped hearing the freon filling the system as if they had equalized. The gauges read that everything was correct.

    We went back inside. The air at the return was 95, the air coming out of the master bedroom register was 70. So we were getting good temperature drop. But the room wasn't cooling down. So we went on the roof and changed the fan speed from low to high to get more air flow.

    On Saturday night the AC functioned as it should, it would run for a few minutes (less than 5) several times an hour. However, on Sunday morning once the outside temperature got over 85, and the inside temperature went over 83 the AC system stopped pulling the temperature down. The AC ran non-stop and couldn't cool the room.

    So for the past several days I have been really frustrated. I am not sure what is happening. At night - The nights are only cooling off to the 70's - the system runs great. But during the day it cannot maintain the temps (office temp of 83/ bedroom temp of 88). Day time temps are in the low triple digits.

    Any thoughts, ideas, suggestions ?

    Thanks again.

    Dave B

  2. #2
    Join Date
    Jun 2011
    Location
    sfv california
    Posts
    110
    hire a pro not an engineer

  3. #3
    Join Date
    Jan 2008
    Posts
    2,127
    Not to knock your friends, but you really need someone over there who can properly diagnose a system.
    "Probably low on R-22" is not a diagnosis, and "the gauges read that everything was correct" is not a proper repair.
    Super heat and sub cool need to be measured, along with many other parameters.
    "Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler

  4. #4
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,376
    If you left the panels off to check for coil freezing, and you had air blowing everywhere, there's no way you got reasonably accurate gauge readings.

    That's aside from any discussion regarding superheat and subcooling data, as 2old2rock has already mentioned.

    So what you have is three people who've had eyes on this system and no solution. You need one set of SEASONED eyes to solve your problem.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

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